And by 2050 this degradation could reach nine-tenths, unless the world’s nations take urgent action. But by that time an estimated 700 million people could have been displaced because of all the implications of this debasement of what was once rich natural landscape.

A new edition of the World Atlas of Desertification, just published by the European Commission, spells out the scale of the problem: an area almost half the size of the European Union is each year in some way damaged by erosion, overgrazing, salinisation, desiccation or human exploitation.

Although the continents most at hazard are Asia and Africa, even the temperate nations of the European Union are affected: around 8% of the land of the member states in southern, eastern and central Europe is affected by desertification.

The word itself is a catch-all term: the editors of the Atlas themselves call it a nebulous and all-encompassing concept that defies physical description. But they choose the term degradation and make their meaning clear: they are talking about soil erosion by wind and rain; they are talking about deterioration of the properties of the soil, and they are talking about the loss of natural vegetation.

In their definition, in a degraded landscape, natural ecosystems cannot supply the essential goods and services to which humans have become accustomed.

These include the supply of food, forage, fuel, building materials; fresh water for humans and their livestock, for irrigation and for sanitation; control of agricultural pests, nutrient recycling, the purification of air and water, the moderation of extreme weather, the protection of biodiversity and other benefits.

And, of course, all the challenges presented by the expansion of both human population and national economies are heightened by global warming and climate change as a consequence of the fossil fuel combustion that adds greenhouse gases to the atmosphere.

What is new is the level of detail and confidence in the information in the new edition of the Atlas, along with extra focus on the human impact on the planet: an impact so marked that many earth scientists now use the term Anthropocene to describe the present geological epoch.

The European Commission has already charted population growth and the explosion of the cities with a new Atlas of the Human Planet.

The latest study calculates the economic cost of soil degradation and climate change as a threat to global food supplies: the two together could lead to a drop in global crop yields by about 10% by 2050.

Most of this will be in India, China and sub-Saharan Africa: in this last region, land degradation could actually halve agricultural output. And by 2050, another two billion people will have been added to the planetary population.